Means for transforming light impulses into current impulses



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Patented Dec; 6, 1932 UNITED STATES- PATENT OFFICE THEODORUS HENDRIX NAKKEN, F BJROOKLYN, NEW YORK, ASSIGNOR TO NAIKKEN PATENTS CORPORATION, A CORPORATION OF DELAWARE MEANS FOR TRANSFORMING LIGHT IMPULSES INTO CURRENT IMPULSES Application filed October 27, 1928. Serial No. 315,562.

The invention herein, like that described in my prior Patent No. 1,522,070, relates to the changing of light impulses into substantial current impulses of practical value. In both cases this phraseology is employed to distinguish from those devices which merely measure a light value in terms of an electrical constant or manifestation. Speaking of the subject from another viewpoint, the aforementioned invention relates exclusively to that art in which a light variableeither in the form of light itself, or a record of variable light transparency must be transformed into a corresponding power manifestation capable of practical use. More particularly this invention applies to the art of telephotography, including perhaps the least important, television, that art which is commonly known as talking moving pictures, the art of sorting different articles in accordance with their light values in rapid succession, and that which is perhaps the most important art of all, the transmission of intelligence in facsimile. I

In all these inventions, the basic thought prevailing is the utilization of a change itself in a static condition, to effect a corresponding change in a power manifestation, such as a flow of current. More particularly, it

contemplates the utilization of. an actualchange inpotential of a photo-electric body (or ofisomething the static potential of which is determined by electrons emitted by said photoelectricbody) to effect itself a correspondiig change in the flow of current. I employ. these statements in contradistinction to the u ilization of kinetic energy derived from a hoto-electric current itself, to be amplifiediinto a current variation.

In carrying out the basic thought in all my inventions it is an object so to combine and correlate the grid or controlling element of a current flow controlling device with some other part, the static condition ofwhich is dependent upon the emission or shedding of electrons in response to a light impulse by a photo-electric body, at the same time providing me ans for and-arranging for the resupplyingv of electrons to replace those which have been emitted in response to a preceding light impulse or preceding light impulses, in such a way that each successive light impulse within its own time interval may effect v an actual change in the static potential either of the photo-electric body itself, or of that thing the static condition of which responds to the electrons emitted from the photoelectric body.

In my previous patent referred to above,

I disclosed one form of link-means for assoclating the thing, the static condition of which was changed in response to light impulses,

tric body and a grid which may be combined in the whole as a result of the utilization of a condenser for. the link-means in the place and stead of a direct conductive connection.

In the invention disclosed in my'previous patent I disclosed the utilization of a single high resistance functioning both for the purpose of stabilizing the grid of an amplifying triode array and for serving in the resupply of electrons to the photo-electric body. In

the invention disclosed herein, it is an ob-' jective to separate these two functions and to provide approved means for making possible the separation of these functions.

A further object of the invention is to provide novel and varied means for employing a photo-electric body in combination with the triode amplifier'for the purpose of transforming light impulses into electric current impulses.

More specifically, the objects of my invention will be pointed out in the accompanying claims, which claims are directed to illustrative embodiments of my invention described in the following specification in connection with the accompanying drawings which form a part hereof.

In the drawings in Fig.1 is a diagram of one form of my invention; Fig. 2 is a similar diagram of a modified form of my invention; Fig. 3 is a similar diagram of a second modification; Fig. 4. is a similar diagram of a third modification; Fig. 5 is a similar diagram showing another modification in which the potential variations of the anode of the photoelectric cell are employed to control the grid potential; Fig. 6 is a diagram similar to that of Fig. 5 showing a modification; Fig. 7 is a. diagram showing a modification in which a space charge is employed; and Fig. 8 is a diagram similar to that of Fig. 7 in which the photo-electric body is disconnected.

' Referring now more in detail to the drawings,in Fig. 1 the usual glass envelope 1 of a photo-electric cell encloses a photo-electric cathode-body 2, which may be made of any of the photo-electrically active substances, such as rubidium, potassium, caesium, etc., and a cooperating anode 3. The usual glass envelope 4 completes the enclosure of the usual vacuum tube amplifier or triode including the usual elements-the cathode shown in the form of a filament F, the grid G and a plate P.

The plate circuit 8 of the triode amplifier contains a translating device 9 which of 7 course is understood as. to indicate anyde- ,anode body 3 is positive. If-now light itavice to be actuated by the plate currentfor example, the primary coil of 'an inter-stage transformer. A battery 10 controlled by the usual rheostat R serves to supply the energy for the filament F, and is preferably connected to with the usual B battery 11 and the C battery 12, provided for the operation of the triode amplifier. The'anode 3 is connected to wire '5,which wire maybe attached over the connection 6 directly to the plate lead 8. Or the connection 6 may be omitted and the anode be connected by a sep-,

arate lead to any point of the B battery 11 directly. By the use of the wire 7 a selection of the desired positive potential for the anode B may be effected. The grid G of the vacuum tube is connected-to wire 14' and consequently the grid G is connected through grid leak resistance 13 and wire 20 with the side of theC batter 12. A second high resistance 15,. p'refera 1' adjustable, leads from the terminal of C battery 12 through Wire 20 to wire 14 on the opposite side ofthe pulses fall upon the body 2 it will instantly emit a definite number of electrons, which number is dependent upon the amount of light which falls upon the body. This emissionof electrons causes the body to lose part of its negative charge and thus its potential is changed to an extent proportional to the light quantity causing this emission. This potential change of the cathode-body 2 is transferred instantaneously over condenser 16 which serves as a link-means to the grid G of amplifier 4, and therefore will cause a comparatlvely large current variation in plate circuit 8. This current variation becomes manifest in the translating device 9.

The emission of electrons by the photoelectric body 2 would rapidly exceed the supply of electrons available for emission in that body if some precaution were not taken to supply new electrons for purposes of emission. This purpose is served by the high resistance 15 which may be varied to accord with the use to which the tube is put. This high resistance 15 allows electrons provided by the string of batteries to reach the cathode-body 2, thus restoring o1 tending to restore its original potential. The higher the value of this resistance 15, the less readily electrons are resupplied, and therefore the size or value of this resistance is actually determined by the amount of electrons normally emitted by the cathode-body 2 under the influence of the light impulses to which it is being subjected. It is bus of great advantage to give resistance 5 a very high value when the light impulses to be translated are exceedingly feeble and when few electrons are shed, while, on the other hand, strong light impulses make it advantageous to use a lower value for the resistance 15. The advantage of this arrangement including the condenser 16 as a part of the link-means connecting the cathode-body 2 with the grid G over an arrangement in which a direct conductive connection serves as the link-means between the photo-electric body 2 and the grid G is that when the condenser is employed the resistances 15 and 13 may be proportioned respectively, so that 15 is of the est value for the resupply of electrons to the cathode-body, while the resistance 13 can be of the value best adapted to maintain proper functioning of the triode amplifier; whereas if the condenser 16 were not employed, the two resistances 15 and 13 would become functionally a single unit and could not be separately proportioned to accord with the'desired individual functions. With the direct conductive connection between the cathode-body and the grid, a single leakage resistance such as 13 functions both as the device for the recharging of the'photo-electric body 2 and as the grid leak for the vacuumtube.

' In Fig. 2 I have repeated exactly the same circuit as that shown in Fig. 1, except that the resistance 15 has been replaced by a variable high inductance 15 and the resistance 13 has been replaced by an inductance 13'. The impedancevalue of the inductance 15 may be regulated, depending upon the frequency of light impulses falling upon the body 2 to provide the desired rate of resupply of electrons to the body 2. This impedance serves as a limiting factor for the resupply of electrons for the photo-electric body 2 by introducing a time lag. Also impedance 13' may be proportioned so as to maintain a proper biasing for and the supplying of the desired leakage path for the grid G.

In Fig. 3, employing the same circuit and permitting of the same modifications as is the case in Fig. 1 and in Fig. 2, I have re placed the resistance 15 with a tuned high frequency circuit 15 which comprises preferably an air core inductance cl and a variable condenser e connected inparallel and at the opposite ends of this parallel circuit respectively to the previously described wires 14 and 20. This parallel circuit should be tuned to be opaque tothe passage between wire 15 and wire 20 of high frequency impulses which correspond to the light impulses impinging upon the photo-electric body 2.-

The essential advantage of the provision of this opaque tuned high frequency parallel circuit is to make impossible any loss in 1m- -parting high frequency potential changes from the photo-electric body to the grid. The resupply of electrons, flowin at a constant rate to the photo-electric bo y through the inductance d is not checked at all by inductance d and no resistance is necessary at all. 4

Again in this same figure .the simple resistance 13 has been replaced by another tuned parallel circuit 13" like that of 15f, but comprising within itself coil d connected in parallel to condenser e. The essential urpose of the tuning of this parallel circuit is likewise to prevent the bypassing of energ from the conductor 14 away from the grid In the modification of Fig. 4, the import-- tance of the use of the opaque tuned circuit is emphasized as shown by the fact that the condenser 16 can be and has been omitted.

The wire 14 directly connecting the photoelectric body 2 with thegridG, while the single tuned parallel circuit 15"" comprising the inductanced and the variable condenser e is connected directly across from the conductor 14 to the conductor 20. This parallel circuit is tuned to be opaque to the passage of energy at the frequency of the light impulses impinging upon the, photo-electric body 2. In each of-the' four cases just described in connection with Figs. 1, 2, 3 and .4, and, in fact modifications of in connection with all the this application, I arbitrari ing 1y designate'each of the things, namely, the

resistances 13 and 15, the impedances 13' and 15, the opaque tuned circuits 1 3 and 15" of the opaque tuned circuit 15' a restrictor. I employ the word restrictor-for the purpose of designating the things which function as Ihave just described in connection with Figs. 1 to 4 inclusive generically in the claims, and not for reasons of limitation in any sense whatsoever.

In the modification of Fig. 5, the cathodebody is connected by lead 33 which is a conductiveconnection directly to the conductor 20 and thence to the side of the battery system whereby the photo-electric body 2 is, as it were, constantly supplied with a full charge of electrons so that it is always substantially at the same uniform potential. In this modification the anode 3 is the element of the photo-electric cell, the potential of which controls the triode amplifier 4 by electrio connection with its grid G. In this circuit the wire 5 leads from the anode 3 through a free path for the interchange of potential impulses to the grid G. In this case the linkmeans-1s 1n the form of wire 5, condenser 16 and wire 14. In order to prevent the buildmg up of an invariable negative potential upon the anode 3 due to electrons emitted from the cathode-body 2, a major dissipation of electrons from anode 3 is provided for b means of the variable high resistance 15, the far end of which may be connected either through the lead 6 with the plate circuit 8 or by bringing the lead 6 over aconductor 7 to any desired posltlve point on the battery svstem. In a circuit of this modification, the grld leak 13 extends, as in Fig. 1, from the conductor 14' to the battery 20. I

F g. 6 1s a repeat of the circuit of Fig. 5

showing how the restrictors may take the form of impedances 15 and 13' in the same Likewise it is to be understood that the restrictors may take the form of the tuned parallel circuit restrictors described in connection with Figs. 3 and 4which are applicable for thesame functioning.

In Fig. 7 100 is a glass bulb capable of maintaining a vacuum and containing a photo-electric cathode-body 2 constructed of any of the approved photo-electric materials.

Also within the bulb 100 is a local source 41 I of electrons shown in the form of an electron emitting filament supplied with energy in the usual way from a suitable source such as the A battery controlled by the usual resistance R and switch S. 40 indicates any approved form of triode amplifier including plate P, grid G,'filament or cathode F. 8 is the plate circuit including translating device 9 and supplied with energy from the usual B battery 11 or its equivalent. In the showillustrated the filament F is controlled by the local circuit 41 from A battery 10 through responding current leak resistance 13 and lead 42 through C bat-v teryl2 and wire 20 to the negative side of A battery 10. It is preferred that the elec-v tron-supplying filament 41 be of the low temperature type incapable of emitting light, relying for the emission of electrons upon its chemical character or upon the chemical character of a coating.

In this system the photo-electric cathodebody 2 relies entirely upon the space charge within the bulb 100 generated by the electron emitter 41 for its supply of electrons. Without light falling upon the cathode-body 2, or with constant light falling upon the cathodebody 2, and with the filament 41 emitting electrons, the photo-electric body 2 will take on a constant negative potential dependent upon the electrons received from the space charge. In the event that light impulses are received by the photo-electric body2 electrons are shed from this photo-electric body in direct proportion to the quantity of light received upon each light mpulse, in consequence of which the potential of this photo-electric body varies proportionately to the light impulses received. These potential changes are conveyed over hnk-means 14, 16,14 to the grid which, in accordance with the usual functioning of the triode amplifier, produce ourimpulses through the translating device 9 of the plate circuit 8. In the use of this system it is interesting to note the continuance of operation in response to received light impulses even after the electron-emitter 41 has been de-energized. It is to he understood that in this circuit the resfrictor 13 shown in Fig. 7 as the usual grid leak may take the form of the inductance 13'- or of a tuned opaque resistor 13".

Fig. 8 shows a modification of the system of Fig. 7 in that an 'anode'or collector 300 is added to receive electrons emitted from the photo-electric body 2 which is entirely conductively disconnected from all the rest of the system. In the modification of this circuit, the link-means 14, 16, 14' connects this anode or collector 300 with the grid G, while animpedance 13 has been shown replacing the resistance 13' and a restrictor 15 in the form of a high ohmic resistance is connected between the anode 300 and any suitable positive point on the battery system. It is of course'to be understood that this restrictor 15 may take on the form of 15 or 15" as in the other figures. In the operation of the modification of this circuit shown in Fig. 8, the varying potential of the anode 300 is utilized to control the grid G, while the variations in the potential of the anode 300 are dependentupon the electrons shed from the photo-electric body 2, which electrons shed from the photo-electric body 2 are in direct proportion to the quantity of light received by it from the light impulses. Although I have shown in my various figures a separate envelope for the photo-electric cell and a second separate envelope for the cooperating triode amplifier, it is to be understood that in substantially all instances onebulb or envelope may enclose both the elements of the photo-electric cell and the triode amplifier, the functioning of the circuits which I have described being independent ofthe envelope employed. There are many instances in which it is highly preferable to employ a single envelope for the elements of the triode amplifier, also for the elements of the photo-electric cell, and I have pointed out this feature in my prior patent referred to above. The principal reason for the enclosing of all elements in the same bulb is to make possible the use of short connections so that as nearly as possible a true static potential control of the grid of the triode amplifier may be had from the photo-electric body. This is particularly apparent when one considers the infinitesimally small amounts of energy represented by the'electrons emitted in response to a light impulse. I have found in practice that the usual disturbances received by unshielded wire of any substantial length are greater than the usual amounts of energy to be employed in response to a light impulse. The art of transforming light impulses into current impulses is radically different from that of measuring a quantity of light. The radical difi'erence is because of the usually infinitesimally small time interval between the light impulses or, in other words, the normal high frequency of the light impulses to be transformed.

What I claim and desire to secure by United 1 States Letters Patent is 1. Means in combination for transforming light impulses into electric current impulses comprising a cathode, a grid and a plate, a

plate circuit including a source of current for the traverse of said electric current impulses; a photo-electric body adapted to be subjected to light impulses constituting the cathodeelectrode of a photoelectric couple; an envelope for maintaining said body in a cooperative atmosphere; an anode within said envelope and within said envelope electrically disconnected and separated from said body and constituting the second electrode of said photoelectric couple; provisions tending to produce and maintain a negative normal potential for said body but themselves incapable of maintaining said potential when said body is being subjected to light; and a link-means including a condenser electrically connecting said body and said grid and adapted to impart potential variations to said' grid corresponding to those which take place on said body.

2. The combination as characterized in claim 1 and further specified by the fact that a high resistance is connected between said body and said cathode.

' 3. In combination, a photo-electric couple having an envelope to maintain it in a cosaid anode; and a link-means including a condenser electrically connecting said cathode-body and said grid and adapted to'impart potential variations to said grid corresponding to those which take place on said body in response to said light impulses, whereby appreciable corresponding impulses in electron-flow to said plate are efiected.

4. In combination, a photo-electric couple having an envelope to maintain it in a cooperative atmosphere and comprising a cathode-body, adapted to be subjected to light impulses, and an anode adapted to receive theelectrons shed by said cathode-body, said anode and said cathodebody being electrical- 1y disconnected Within said envelope; a cathode, a grid and a plate and a plate circuit for the passage of current impulses;

provisions tending to produce and maintain a negative normal potential for said cathodebody; and a link-means including a condenser electrically connecting said anode and said grid and adapted to impart potential variations to said grid corresponding to those which take place on said anodedue to 1t)h1 a1 reception of electrons from said cathodeo y. I

5. In combination, a photo-electric couple having anienvelope to maintain it in a cooperative atmosphere and comprising a cathode-body, adapted to be subjected to light impulses, and an anode adapted to receive the electrons shed by said cathode-body, said anode and said cathode-body being electrically disconnected within said envelope; a cathode, a grid and a plate and a plate circuit for the passage of current impulses; provisions tending to produce and maintain a negative normal potential for said cathode-body; and

a link-means including a condenser electri cally'connecting said anode and saidgrid and adapted to impart potential variations to said grid corresponding to those which take place on said anode due to the reception of electrons from said cathode-body; and a leak resistance connected between said linknziaans including acondenser and said catho e.

6. In combination a photo-electric couple comprising a cathode and a separate anode; an envelope adapted to maintain said photoelectric couple in a cooperative atmosphere; a current-strength-controller operating by reason of changes in potential; a link-means including a condenser electrically connecting one electrode of said photo-electric couple with said. current-strength-controller and adapted to impart potential variations to said controller corresponding to those which take place on said electrode; and provisions tending to produce and maintain a negative normal potential for the cathode of said photo-electric couple, but said provisions being incapable of maintaining an unchanged normal potential upon that electrode of said photo-electric couple which is electrically connected with said current-strength-controller.

'Z. In combination a photo-electric-cathode-body exposable to light variations and a separated anode. adapted to receive electrons emitted by said cathode-body; an envelope adapted to maintain said photoelectric cathode-body and said anode in a cooperative atmosphere; a grid which controls a current flow by reason of potential; and a link-means including a condenser between said cathodebody and said grid to control the potential of said grid by potential changes in saidcathode-body; andprovisions in addition to said link-means including a condenser tending to body.

8. Means in combination for transform-' ing light impulses into electric current impulses including an electron emitting cathode, a grid and a plate; a plate circuit including a source of direct current and forming the circuit for said current impulses; a photoelectric cathode-body; a separated anode for said photo-electric cathode body; an envelope for maintaining a cooperative atmosphere about said cathode-body and said anode; an electric connection between said photo-electric cathode-body and said grid including a condenser and of such character as to impart substantially instantaneously a change of potential in said photo-electric cathode-body to said grid; provisions in addition to said electric connection between said photo-eleccorresponding appreciable current changes in said plate circuit.

9. In a system for transforming light impulses into electric current impulses, a photoelectric couple comprising two separated electrodes-a photo-electric body and a cooperative anodesaid body being adapted to receive light impulses; an envelope adapted to electrode of said photo-electric couple which' is connected with said link-means and said cathode of said triode amplifier and between said grid and said cathode of said triode amplifier, said impedance devices being maintained independent one from the other by said condenser with respect to their conductivity of direct current and said impedance devices being each of such kind and value as to permit a substantially undiminished interchange of potential variation between said grid and said electrode which is connected with said link-means.

10. The combination as characterized in claim 9 and further specified by the fact that one of said impedance devices is in the form of a high ohmic resistance.

11. The combination as characterized in claim 9 and further specified by the fact that one of said impedance devices comprises inductance of avalue for opposing the passage of energy impulses corresponding to the frequency of said light impulses.

12. The combination as characterized in claim 9 and further specified by the fact that one of said impedance devices comprises a parallel tuned circuit including capacity and inductance tuned to be substantially opaque to the passage of energy impulses corresponding to the frequency of said light impulses.

13. In combination an apparatus for transforming light impulses into appreciable current impulses comprising a photo-electric couple including two electrodes-a photoelectric body and a cooperative anode: .a triode amplifier comprising a cathode, a grid and a plate; a plate circuit in which said current impulses are adapted to flow: a connection between one of the electrodes of said photoelectric couple and said grid for imparting thereto potential chan ges corresponding to the potential changes of said electrode and means for stabilizing the average potential of both said grid and said connected electrode of said photo-electric couple comprising an electrical connection leading fromsaid cathode of said triode amplifier both to said grid and to said connected electrode and including a tuned parallel circuit comprising inductance and capacity tuned to be substantially opaque to the passage to said cathode of energy impulses corresponding to the frequency of said light impulses.

14. In combination an apparatus for transforming light impulses into appreciable curthe average potential of both said grid and said connected electrode of said photo-electric couple comprising an electrical connection leading from said cathode of said triode amplifier both to said grid and to said connected electrode and including a tuned parallel circuit comprising inductance and capacity tuned to be substantially opaque to the passage to said cathode of energy impulses corresponding to the frequency of said light impulses.

15. An amplifying system for transforming light impulses into appreciable electric current impulses comprising a photo-electric body, a cooperative local source of free electrons; a triode amplifier including a cathode, a grid and a plate; an electrical connection including a condenser connecting said photoelectric body and said grid; a stabilizing resistor for said grid connected between said electric body whereby light impulses falling upon said photo-electric body impart corresponding potential impulses to said grid and a source of electric energy and a translating device completing a plate circuit for said plate. p

16. A photo-electric cell comprising a photo-electric body, a local emitter of free electrons in cooperative relationship with said photo-electric body and an anode in cooperative relationship with said photo-electric body, said photo-electric body being free from all circuit connections except that which may be provided by space charge; a triode amplifier comprising a cathode, a grid and a plate: a plate circuit for said triode amplifier including a suitable source of energy and said grid and said cathode with said anode of said photo-electric cell and respectively selected portions ofsaid biasing means being maintained functionally independent by sai condenser and themselves being proportioned and of a quality so as to maintam a substantial undiminished interchan e of potential fluctuations between said 9.110 e and said grid through said condenser.

THEODORUS H. NAKKEN, 

